Contrasting responses of small mammal diversity to landscape composition and configuration in Mediterranean agroecosystems

The effects of land-use composition and spatial configuration on biodiversity have been widely assessed in agroecosystems, yet whether complementary dimensions of diversity respond similarly to these landscape attributes remains unclear. This limitation is particularly evident for vertebrate taxa that are difficult to survey at landscape scales, including small mammals, which play key roles in agroecosystems. Here, we used barn owl ( Tyto alba ) pellet analysis to investigate how landscape structure shapes multiple dimensions of small mammal diversity in Mediterranean agroecosystems in northeastern Portugal. We characterized small mammal assemblages at 40 nest sites using morphological identification and quantified diversity with Hill numbers (q = 0, 1, 2), capturing complementary dimensions of diversity, from species richness to dominance-weighted diversity. We then related variation in landscape composition and configuration to small mammal diversity metrics using generalized linear mixed models. Species richness (q0) showed the strongest response to landscape variables, declining with increasing olive grove cover and shape complexity of olive groves and urban areas, while increasing with shrubland cover and chestnut woodland patch density. Abundance-weighted diversity metrics showed weaker and more differentiated responses, with diversity of order q1 (common species) showing a unimodal relationship with agricultural cover and a declining trend with increasing shape complexity of agricultural land, and q2 (dominant species) declining at high levels of agricultural cover, while showing a declining trend with its shape complexity and a positive trend with wetland density. Overall, our results reveal contrasting responses among richness, common-species and dominant-species diversity to landscape composition and configuration, highlighting the value of integrating multiple diversity measures in agroecosystem assessment and management.